The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Name:	us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goodwill and other intangible assets - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2019 USD ($) reporting_unit	May 31, 2018 USD ($)	May 31, 2019 USD ($)	May 31, 2018 USD ($)
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets \| $	$ 142	$ 146	$ 415	$ 363
Retail Pharmacy International
Finite-Lived Intangible Assets [Line Items]
Number of reporting units \| reporting_unit	2
Boots Reporting Unit \| Retail Pharmacy International
Finite-Lived Intangible Assets [Line Items]
Reporting unit, fair value in excess of carrying amount (as a percent)	9.00%		9.00%
Pharmacy Licenses \| Retail Pharmacy International
Finite-Lived Intangible Assets [Line Items]
Reporting unit, fair value in excess of carrying amount (as a percent)	5.00%		5.00%